Recently, a printer which can perform printing on both faces of a sheet has been developed. Printers of this kind include: a printer in which print heads respectively for front/back faces are separately disposed, as disclosed in Japanese Patent Publication No. 3-53955A; and that which comprises a mechanism for reversing a whole sheet to enable a single print head to perform double-sided printing, as disclosed in Japanese Patent Publications Nos. 59-31178A and 61-89876A.
In a printer of the type in which print heads respectively for front/back faces are separately disposed, however, a space for disposing the two print heads is necessary, and therefore down-sizing of the printer is obstructed. Moreover, there is a disadvantage that the number of parts is increased and the cost is high.
In a printer of the type which comprises a mechanism for reversing a whole sheet, the reversing mechanism is a complicated mechanism which reverses a sheet while transferring the sheet among plural roller pairs, thereby causing a disadvantage that the jam (sheet jamming) rate is high. A sheet reversing path which is sufficient for reversing a whole sheet must be ensured, and therefore down-sizing of the printer is obstructed. Moreover, there is a disadvantage that the time required for reversing a sheet cannot be neglected and causes a disadvantage that the throughput of the printer is lowered. Furthermore, there is another disadvantage that a sheet which is longer than the sheet reversing path cannot be reversed.
It is an object of the invention to provide a printer which comprises a sheet reversing mechanism, which can perform printing on both faces of a sheet by a common print head, and in which reduction of the number of parts, prevention of a transport failure, and the like are realized by reversing the sheet while the sheet is clamped by one transporting roller pair.